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diff --git a/engines/tony/mpal/expr.cpp b/engines/tony/mpal/expr.cpp
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+++ b/engines/tony/mpal/expr.cpp
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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ *
+ */
+/*
+ * This code is based on original Tony Tough source code
+ *
+ * Copyright (c) 1997-2003 Nayma Software
+ */
+
+#include "tony/mpal/mpal.h"
+#include "tony/mpal/memory.h"
+#include "tony/mpal/mpaldll.h"
+#include "tony/tony.h"
+
+namespace Tony {
+
+namespace MPAL {
+
+
+/**
+ * Duplicate a mathematical expression.
+ *
+ * @param h				Handle to the original expression
+ * @retruns		Pointer to the cloned expression
+ */
+static byte *duplicateExpression(MpalHandle h) {
+	byte *orig, *clone;
+
+	orig = (byte *)globalLock(h);
+
+	int num = *(byte *)orig;
+	LpExpression one = (LpExpression)(orig+1);
+
+	clone = (byte *)globalAlloc(GMEM_FIXED, sizeof(Expression) * num + 1);
+	LpExpression two = (LpExpression)(clone + 1);
+
+	memcpy(clone, orig, sizeof(Expression) * num + 1);
+
+	for (int i = 0; i < num; i++) {
+		if (one->_type == ELT_PARENTH) {
+			two->_type = ELT_PARENTH2;
+			two->_val._pson = duplicateExpression(two->_val._son);
+		}
+
+		++one;
+		++two;
+	}
+
+	globalUnlock(h);
+	return clone;
+}
+
+static int Compute(int a, int b, byte symbol) {
+	switch (symbol) {
+	case OP_MUL:
+		return a * b;
+	case OP_DIV:
+		return a / b;
+	case OP_MODULE:
+		return a % b;
+	case OP_ADD:
+		return a + b;
+	case OP_SUB:
+		return a - b;
+	case OP_SHL:
+		return a << b;
+	case OP_SHR:
+		return a >> b;
+	case OP_MINOR:
+		return a < b;
+	case OP_MAJOR:
+		return a > b;
+	case OP_MINEQ:
+		return a <= b;
+	case OP_MAJEQ:
+		return a >= b;
+	case OP_EQUAL:
+		return a == b;
+	case OP_NOEQUAL:
+		return a != b;
+	case OP_BITAND:
+		return a & b;
+	case OP_BITXOR:
+		return a ^ b;
+	case OP_BITOR:
+		return a | b;
+	case OP_AND:
+		return a && b;
+	case OP_OR:
+		return a || b;
+	default:
+		GLOBALS._mpalError = 1;
+		break;
+	}
+
+	return 0;
+}
+
+static void solve(LpExpression one, int num) {
+	LpExpression two, three;
+
+	while (num > 1) {
+		two = one + 1;
+		if ((two->_symbol == 0) || (one->_symbol & 0xF0) <= (two->_symbol & 0xF0)) {
+			two->_val._num = Compute(one->_val._num, two->_val._num, one->_symbol);
+			memmove(one, two, (num - 1) * sizeof(Expression));
+			--num;
+		} else {
+			int j = 1;
+			three = two + 1;
+			while ((three->_symbol != 0) && (two->_symbol & 0xF0) > (three->_symbol & 0xF0)) {
+				++two;
+				++three;
+				++j;
+			}
+
+			three->_val._num = Compute(two->_val._num, three->_val._num, two->_symbol);
+			memmove(two, three, (num - j - 1) * sizeof(Expression));
+			--num;
+		}
+	}
+}
+
+
+/**
+ * Calculates the result of a mathematical expression, replacing the current
+ * value of any variable.
+ *
+ * @param expr				Pointer to an expression duplicated by DuplicateExpression
+ * @returns		Value
+ */
+static int evaluateAndFreeExpression(byte *expr) {
+	int num = *expr;
+	LpExpression one = (LpExpression)(expr + 1);
+
+	// 1) Substitutions of variables
+	LpExpression cur = one;
+	for (int i = 0; i < num; i++, cur++) {
+		if (cur->_type == ELT_VAR) {
+			cur->_type = ELT_NUMBER;
+			cur->_val._num = varGetValue(cur->_val._name);
+		}
+	}
+
+	// 2) Replacement of brackets (using recursive calls)
+	cur = one;
+	for (int i = 0; i < num; i++, cur++) {
+		if (cur->_type == ELT_PARENTH2) {
+			cur->_type = ELT_NUMBER;
+			cur->_val._num = evaluateAndFreeExpression(cur->_val._pson);
+		}
+	}
+
+	// 3) algebraic resolution
+	solve(one, num);
+	int val = one->_val._num;
+	globalDestroy(expr);
+
+	return val;
+}
+
+
+/**
+ * Parses a mathematical expression from the MPC file
+ *
+ * @param buf				Buffer containing the expression to evaluate
+ * @param h					Pointer to a handle that, at the end of execution,
+ * will point to the area of memory containing the parsed expression
+ * @returns		Pointer to the buffer immediately after the expression, or NULL if error.
+ */
+const byte *parseExpression(const byte *lpBuf, MpalHandle *h) {
+	byte *start;
+
+	uint32 num = *lpBuf;
+	lpBuf++;
+
+	if (num == 0)
+		return NULL;
+
+	*h = globalAllocate(GMEM_MOVEABLE | GMEM_ZEROINIT, num * sizeof(Expression) + 1);
+	if (*h == NULL)
+		return NULL;
+
+	start = (byte *)globalLock(*h);
+	*start = (byte)num;
+
+	LpExpression cur = (LpExpression)(start + 1);
+
+	for (uint32 i = 0;i < num; i++) {
+		cur->_type = *(lpBuf);
+
+		// *(lpBuf + 1) contains the unary operator, unused => skipped
+		lpBuf += 2;
+
+		switch (cur->_type) {
+		case ELT_NUMBER:
+			cur->_val._num = (int32)READ_LE_UINT32(lpBuf);
+			lpBuf += 4;
+			break;
+
+		case ELT_VAR:
+			cur->_val._name = (char *)globalAlloc(GMEM_FIXED | GMEM_ZEROINIT, (*lpBuf) + 1);
+			if (cur->_val._name == NULL)
+				return NULL;
+			memcpy(cur->_val._name, lpBuf + 1, *lpBuf);
+			lpBuf += *lpBuf + 1;
+			break;
+
+		case ELT_PARENTH:
+			lpBuf = parseExpression(lpBuf, &cur->_val._son);
+			if (lpBuf == NULL)
+				return NULL;
+			break;
+
+		default:
+			return NULL;
+		}
+
+		cur->_symbol = *lpBuf;
+		lpBuf++;
+
+		cur++;
+	}
+
+	if (*lpBuf != 0)
+		return NULL;
+
+	lpBuf++;
+
+	return lpBuf;
+}
+
+
+/**
+ * Calculate the value of a mathamatical expression
+ *
+ * @param h					Handle to the expression
+ * @returns		Numeric value
+ */
+int evaluateExpression(MpalHandle h) {
+	lockVar();
+	int ret = evaluateAndFreeExpression(duplicateExpression(h));
+	unlockVar();
+
+	return ret;
+}
+
+/**
+ * Compare two mathematical expressions together
+ *
+ * @param h1				Expression to be compared
+ * @param h2				Expression to be compared
+ */
+bool compareExpressions(MpalHandle h1, MpalHandle h2) {
+	byte *e1, *e2;
+
+	e1 = (byte *)globalLock(h1);
+	e2 = (byte *)globalLock(h2);
+
+	int num1 = *(byte *)e1;
+	int num2 = *(byte *)e2;
+
+	if (num1 != num2) {
+		globalUnlock(h1);
+		globalUnlock(h2);
+		return false;
+	}
+
+	LpExpression one = (LpExpression)(e1 + 1);
+	LpExpression two = (LpExpression)(e2 + 1);
+
+	for (int i = 0; i < num1; i++) {
+		if (one->_type != two->_type || (i != num1 - 1 && one->_symbol != two->_symbol)) {
+			globalUnlock(h1);
+			globalUnlock(h2);
+			return false;
+		}
+
+		switch (one->_type) {
+		case ELT_NUMBER:
+			if (one->_val._num != two->_val._num) {
+				globalUnlock(h1);
+				globalUnlock(h2);
+				return false;
+			}
+			break;
+
+		case ELT_VAR:
+			if (strcmp(one->_val._name, two->_val._name) != 0) {
+				globalUnlock(h1);
+				globalUnlock(h2);
+				return false;
+			}
+			break;
+
+		case ELT_PARENTH:
+			if (!compareExpressions(one->_val._son, two->_val._son)) {
+				globalUnlock(h1);
+				globalUnlock(h2);
+				return false;
+			}
+			break;
+		}
+
+		++one;
+		++two;
+	}
+
+	globalUnlock(h1);
+	globalUnlock(h2);
+
+	return true;
+}
+
+/**
+ * Frees an expression that was previously parsed
+ *
+ * @param h					Handle for the expression
+ */
+void freeExpression(MpalHandle h) {
+	byte *data = (byte *)globalLock(h);
+	int num = *data;
+	LpExpression cur = (LpExpression)(data + 1);
+
+	for (int i = 0; i < num; ++i, ++cur) {
+		switch (cur->_type) {
+		case ELT_VAR:
+			globalDestroy(cur->_val._name);
+			break;
+
+		case ELT_PARENTH:
+			freeExpression(cur->_val._son);
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	globalUnlock(h);
+	globalFree(h);
+}
+
+} // end of namespace MPAL
+
+} // end of namespace Tony